1. Field of the Invention
The present disclosure relates to a travel velocity compensation apparatus for railway vehicles and a method thereof, and more particularly to an apparatus for compensating a travel velocity of a railway vehicle during generation of slide between a wheel of a railway vehicle and a rail, and a method thereof.
2. Description of Related Art
In general, wheels of a railway vehicle and a rail are all made of steel material, and prone to generate a slide (or skip) phenomenon during braking of a railway vehicle due to smaller adhesion coefficient between the wheel and the rail. The slide phenomenon is generated, in a case a braking force is greater than an adhesion coefficient between a wheel of a railway vehicle and a rail, where the wheel fails to rotate but slides due to lock-up state of the wheel. Thus, in a case the slide is generated, a braking distance of a railway vehicle is lengthened to wear the wheel due to friction between the wheel and rail.
In general, a wheel slide is detected by comparing values of four speed sensors mounted on a wheel axis of railway vehicle and values of four speed sensors mounted on an adjacent railway vehicle. That is, a rotating velocity of a wheel and a travel velocity of a railway vehicle are calculated by using a pulse signal measured by a sensor while the wheel axis of a railway vehicle is rotated, a braking force is calculated by using an air pressure data measured by a braking cylinder, and the slide is measured by measurement of a braking air pressure.
However, the abovementioned method suffers from disadvantages in that the slide phenomenon cannot be detected due to there being no difference in the signals measured by the four speed sensors, in a case the slide is simultaneously generated on wheel axes of four railway vehicles because four speed sensors are used.
In general, velocity of a railway vehicle is calculated by using counts of a tachometer mounted on a wheel axis. There are two methods calculating the velocity of railway vehicle. That is, one is to use information of a tachometer mounted on a wheel axis of a railway vehicle, and the other is to obtain a travel velocity of a railway vehicle by integrating acceleration information measured by an accelerometer.
The method of using the information of a tachometer mounted on a wheel axis of a railway vehicle is configured such that a tachometer counts revolution of a wheel while the wheel connected to the wheel axis of the railway vehicle is rotated, an angular velocity of the wheel is obtained from the counted information, and the velocity of the railway vehicle is calculated by multiplying the angular velocity by wheel radius.
However, there occurs a problem in that, the velocity of a railway vehicle cannot be calculated using the angular velocity of the wheel, because the wheel slides due to lock-up state of the wheels, in a case a slide is generated on the wheels. That is, in a case slide is generated, the wheels are not rotated to cause a travel velocity of a railway vehicle to be calculated as zero (0), which in turn generates a big error in calculation of velocity of a railway vehicle.
The method of obtaining a travel velocity of a railway vehicle by integrating acceleration information measured by an accelerometer is disadvantageous in that noise from a sensor during measurement is also integrated during calculation of velocity of a railway vehicle, resulting in deteriorated accuracy.